The field of the invention is generally that of indicators, and more specifically, to an improved miniature telltale module.
Most automotive instrument clusters contain fifteen to twenty-five warning or information indicators (telltales). Packaging these functions as part of an instrument cluster design inhibits the flexibility of the design and creates complexity throughout the assembly.
The instrument cluster housing typically provides the support for the telltale bulbs. The housing also incorporates complex structures to eliminate light leakage (or crosstalk) from adjacent telltales or into the instrument graphics areas.
Telltale bulbs are commonly powered through a flexible circuit which is placed on the back of the instrument case. The size and complexity of the flexible circuit required in each instrument is highly dependent on the telltale arrangement. Flexible circuits, therefore, add cost to the telltale function and increase the number of electrical connections thus decreasing the system reliability.
Current production instrument clusters contain a light bulb and socket for each telltale function. Material and assembly costs to install, test and inspect these bulbs accumulates into a significant portion of the instrument cluster cost because so many are needed. Incandescent bulb life and reliability continues to be an important factor even though bulb and socket design improvements have been made.
Prior Art:
Several types of devices are known which have attempted to solve the problems stated above. By combining several telltale indications or messages into one unit, Pomerantz (U.S. Pat. No. 3,839,701) and Reck (U.S. Pat. No. 3,835,450) both taught the use of a D.C. Motor to rotate a message carrying drum using gears. Mechanical switches were incorporated to stop the motor at the required locations and a lamp was lighted to display the message or image. Both of these devices are complex electro-mechanical assemblies containing many parts, some of which are required to be precise (i.e. gears). This forces the cost of these devices to be high and thus they have not been used extensively.
Fales (U.S. Pat. No. 3,660,814) teaches a simpler method of actuating a message carrying drum but like Pomerantz and Reck the assembly is large and therefore consumes too much space and thus is difficult to package within the instrument cluster. Also, the drum construction creates a large inertial load on the actuator thus requiring the Fales actuator to be heavily damped (with viscous fluid) to eliminate overshoot and ringing. This presents a response problem similar to the D.C. motor actuation and adds the need for the emergency indicator and it's required control logic. The extended period of time that the actuators are driven also increases the power consumption of the unit. In fact, Fales powers the actuator and the lamp all the time that a fault condition is signaled.
The cost and design flexibility problems of current approaches coupled with the fact that the prior art has not provided acceptable solutions calls for a new concept.
The present invention provides this new concept by disclosing a miniature telltale module that has the capability of containing a large number of images or messages. Further, this module is designed to be low cost and provides a variety of packaging options to enhance flexibility.